To increase the capacity of a watermarking system, compressing the original watermark into a smaller size is one of the reasonable solutions. In this chapter, a VQ-based coding procedure   with an index-assignment procedure is illustrated for general watermarking schemes to enlarge their capacity. It employs the VQ operator to compress the gray watermark and adjusts the compressed result according to an index table. Then, a genetic index assignment (GIA)  procedure is introduced to find a better way to assign the indices in order to have better imperceptibility.
Feng-Hsing Wang, Jeng-Shyang Pan, L. Jain
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